An exhaust gas discharged from an internal combustion engine such as a diesel engine contains nitrogen oxide (NOx), which is an air pollutant. One known exhaust gas purifying system for purifying such an exhaust gas is an exhaust gas purifying system configured to provide an SCR (Selective Catalytic Reduction) type catalyst in the exhaust flow path and to jet urea water, which is a reducing agent, in the exhaust gas upstream of the catalyst. Such urea water jetted into the exhaust gas is hydrolyzed by heat of the exhaust gas. And, ammonia (NH3) generated by the hydrolysis of the urea water is supplied to the catalyst together with the exhaust gas. Nitrogen oxide within the exhaust gas reacts with ammonia in the catalyst and is reduced and purified.
In such type of an exhaust gas purifying system, the exhaust gas stirring device for stirring the exhaust gas that flows through the exhaust flow path is disposed upstream of the catalyst, so that a bias does not occur easily in a distribution of the exhaust gas (including a reducing agent) that flows into the catalyst. The exhaust gas stirring device is formed of a single metal plate member into a shape having vanes that protrude from a cylindrical tubular body as disclosed in, for example, Patent Document 1. The metal plate member has a belt part formed in a straight line, and vane parts that protrude from one end-side of the belt part in width direction. The tubular body is formed by cylindrically rolling the belt part of the metal plate member. The vane parts are formed to protrude inwardly from the tubular body.